In the construction of equipment and components for aircraft, there is a fundamental requirement for guaranteed maximum safety and reliability, together with the greatest possible lightness.
In on-board hydraulic systems intended for supplying numerous essential service devices, such as for example servocontrols, brakes, undercarriages and so on, pressure accumulators are components of particular importance.
These accumulators have the function of containing a volume of hydraulic oil kept under pressure by a pressurized gas for supplying a sufficient quantity of oil, even in the case of failure of the compressor installation or of a portion of the supply circuit, to permit essential items of equipment for emergency flight operations to be actuated.
In many designs it has been noted that the accumulators are the components which carry the greatest weight penalty in said hydraulic installations. This is due to the design standards, which impose a fairly high factor of structural safety, and to the particular service loadings for which the accumulators must be designed.
In order to reduce the weight of these components, it is possible to have recourse to steels possessing high structural strength values, but these materials do not provide sufficient fatigue strength and wear resistance, are difficult and expensive to machine, and moreover lead to only moderate reductions in weight.
It is also possible to use material of a composite type, but such materials with the known manufacturing techniques, do not lend themselves to the construction of complicated and asymmetrical forms, as required in accumulators.